1. Field of the Invention
This invention relates to a process of manufacturing a member formed with a shaft-receiving opening by subjecting a compact formed with a through hole and comprising a sinterable powder to liquid-phase sintering.
2. Description of the Prior Art
To utilize the relatively light weight and the high wear resistance of compacts of sintered metal, e.g., in the manufacture of camshafts for controlling the valves of internal combustion engines, Published German Application 3,500,653 proposes the cams or other members to be mounted on the shaft, which members are formed with a shaft-receiving opening, be made by compacting a sinterable powder and, after presintering, they are then shrunk onto the steel shaft to provide a press fit. The succeeding final sintering will then result in a metallurgical bond between the shaft and the shaped member. But that manufacturing process involves the disadvantage that in spite of the press fit it is hardly possible exactly to determine the relative angular position of the compacts during the sintering process by which they are joined to the shaft.
It has already been proposed in Published German Application 3,209,980 to avoid said disadvantages by fitting the presintered compacts on the shaft with a radial play and the compacts are positioned by inserting tubular retaining members with a press fit into aligned bores, which are formed in the shaft and in the compacts. But in that case it is difficult to form the bores in the compacts after they have been presintered. Besides, it is virtually impossible to maintain the dimensions of the compacts during their unrestrained shrinking within the permissible limits.
Finally, it is known from Published German Application 3,907,886 to provide a camshaft with composite cams, which comprise an outer member and an inner member, and to restrict the shrinkage of the inner member particularly in the axial direction in that the inner member has a smaller shrinkage under the sintering conditions than the outer member so that, in addition, a firm metallurgical bond between the two parts will be ensured. Because the joint ton the steel shaft is again established during the liquid-phase sintering, the positioning difficulties described hereinbefore will necessarily arise too.